This invention relates to a form-fill-seal type packaging machine for producing packaged products by bending an elongated bag-making material into a tubular form by means of a former unit while dropping articles to be packaged into the tubularly formed material.
A packaging machine of this kind, for producing bags filled with potato chips, for example, is typically structured such that an elongated bag-making material (the "film") is unwound from a roll and transported downward while it is bent into a tubular form, articles to be packaged are dropped in after the bottom edge of this tubularly formed film is transversely sealed, and the top edge is also transversely sealed thereafter to produce a bag with articles sealed inside. Such a packaging machine is usually provided with a former for guiding the film in a specified direction while bending it such that both its longitudinal edge parts overlap one on top of the other and a chute through which articles to be packaged are dropped into the tubularly formed film after its bottom edge is transversely sealed. Prior art packaging machines, however, were designed to produce bags of only a specified size. If it is desired to produce bags of different sizes by using such a prior art packaging machine, it is necessary to exchange both the former and the chute. Since the former and the chute are normally required to be exchanged separately, the work of exchanging the former and the chute has been a cumbersome process, adversely affecting the work efficiency.
In view of the above, it has been known to unify the former and the chute such that the work of exchanging them can be made simpler and the packaging work efficiency can be improved.
A method of and a mechanism for attaching a prior art former unit will be explained next with reference to FIG. 9, wherein numeral 301 indicates a former unit to be attached to a main frame X of the packaging machine. The former unit 301 comprises a base member 302, columnar members 303 standing up at both side regions of the base member 302 and brackets 304 which are attached to the upper ends of the columnar members 303, extending horizontally for supporting a chute 305 nearly at the center of the base member 302. A former 306 is attached at a position somewhat below where the chute 305 is supported by the brackets 304 so as to surround the chute 305. The base member 302 has two notches 307 formed therein, and the main frame X of the packaging machine is provided with screw holes (not shown) at corresponding positions such that the former unit 301 can be fastened to the main frame X by matching the notches 307 in the base member 302 with these holes and inserting levered screws 308 in them and tightening.
The method and mechanism of the prior art technology described above were not satisfactory because there was the possibility of the screws 308 becoming loose during the course of operation of the packaging machine such that accurate bag-making operation could not be continued. Since two screws must be loosened and then tightened for each exchange operation, furthermore, this prior art technology was unsatisfactory also from the point of view of work efficiency.